Actually, mastectomies were readily being explored as early as the 1800s (and even earlier, although this was before general anesthesia). In fact, the first surgery under anesthesia happened in 1804...and was a mastectomy. I have to question your dismissal of the narrative if you can't even google "history of mastectomies".
"Didn't get what was advertised on the box?" I don't remember you ever being promised anything other that this game contains +18 content.
Whatever the case...I'm pretty sure that I'm not the only one highly dissapointed by Hiro's condition. There's more people companining about it, albeit I'm the only one that is not...well, cowed into faking at least some enthusiasm on the matter.
All in all, it seems like his situation seems a bit forced in, to have that sort of character in the history just for the sake of it. While on its own doesn't detract (nor adds) to his personality, it still feels out of place at the mid 30s.
Just a friendly bit of advice: Don't speak authoritatively on historical matters you lack the intellectual courage to actually learn about.
Trans people are not some modern invention or whatever transphobic garbage you're suggesting here. Hiro's story seems to take place in pre-nazi Germany, which was in fact at the cutting edge of sexual research and queer rights advocacy from foundations such as the Institut für Sexualwissenschaft in Berlin (the very institute whose books were the first the Nazis gathered for book burnings, fyi)
Hiro's identity isn't forced, it fits well with the story's period AND he is precious and I would kill anyone who would try to harm him.
